Cathode ray deflection apparatus



June 13, 1939. H IO. ROOSENSTEIN ET AL 2,161,977

CATHODE RAY REFLECTION APPARATUS Filed Feb. 10, 1937 74 ATTORNEY Patented June 13, 1 939 UNITED STATES PATENT OFFICE CATHODE RAY DEFLECIION APPARATUS Application February 10, 1937, Serial No. 125,158 In Germany January 21, 1936 Claims.

When iron-core coils are used for the magnetic deflection of cathode rays, such as is the case for instance in cathode ray tubes for oscillographic or television purposes, the problem is 5 presented that the deflecting field intensity is not all homogeneous within the air gap of iron core. It need not be stressed particularly that a nonhomogeneous field of this type exerts an influence of varying degree on the individual electronic paths contained in the cathode ray pencil with the result that the concentration of the cathode ray in a deflected state may be impaired under certain circumstances.

In accordance with this invention, the deflecting coils need not be disposed directly on the arms of the iron yoke joined directly to the pole pieces, as is the usual practice of the art. In this known arrangement of the deflecting coils the axes of the two coil halves intersect the axis of tube, but

in accordance with the present proposal the deflecting coils are attached so that a finite distance exists between the axis of one or several of the coils traversed by the deflecting currents and the axis of tube. In consequence thereof, the axis 5 of the :coils and that of the tube are off-set with respect to each other, so that they do not intersect each other, the arrangement being preferably made in the manner, as may be seen from the exemplified embodiments to follow, that the 30 two axes are at right angles to each other without intersecting. Or, expressed in other words, a plane exists containing one axis and with which the other axis forms a 90 angle.

Our invention will best be understood by ref- 5 erence to Fig. 1 in which there is shown the flux distribution about two pole pieces in the air gap. Fig. 2 is one embodiment of our invention. Fig. 3 is another embodiment of our invention. Fig. 4 is a still further embodiment, and Fig. 5 is yet 40 another embodiment. Fig. 6 is a perspective view of the arrangement with a cathode ray tube.

In the embodiment according to Fig. 2, the iron core consists of three legs I0, II and i2, of which the two outer arms support two coils l3, 14, while 45 the inner leg contains the air gap wherein is disposed the cathode ray tube. The flux that would flow through the two external arms, the two magnetic yokes l5, l6 and interior arm l2, would have the approximate distribution within the air gap 5 as illustrated in Fig. 1. But in the arrangement shown of coils l3, H the stray flux of the coils closes partly also through the marginal parts of air gap as may be seen from the stray flux distribution indicated in Fig. 2, with the result that 55 the deflecting field intensity within the air gap is homogeneous to a much higher degree than is the case illustrated in Fig. l. The coil arrangement shown in Fig. 2 wherein the coil axes have a finite distance from the tube axis is accordingly much superior to the coil arrangement used by 5 the prior art on arms l2.

Another embodiment of the new coil arrangement is represented in Fig. 3. Therein the yoke of iron with its legs [0 to i2 and its yokes l5, I6 is indicated by simple lines only to simplify matl0 ters, and in place of the two coils l3, M are provided two coils each, l3, l3" and l4, l4". Also in this case the flux due to the two coils I3, I3" and l4, M" respectively, (one of whose lines of force is indicated in dotted lines) whose course 15 however is not through arm I2, is suitable for imparting homogeneity to the field in the air gap.

In the embodiment according to Fig. 4 corresponding deductions hold as for the case of Fig 3,

the flux due to coils l3, l3", not fiowing through arm l2 (in dotted lines), insuring also the removal of the non-homogeneity of deflecting field.

In the embodiment shown in Fig. 5 there is provided in addition to the arm i2 containing air gap with only a single further arm ill and only one coil l3 traversed by deflecting current. In this case pole pieces I! in air gap are developed in the manner that at the right side the deflecting field has a course still sufilciently homogeneous even at relatively great distance from axis of 30; tube, while on the left side the stray flux of coil l1 eliminates the non-homogeneity of deflecting field as explained with respect to Fig. 2.

The dimensions of the iron yoke for which the stray flux has the correct size in comparison to the flux flowing through arms l2, may be determined by experiments. Also a corresponding distribution of the numbers of ampere-turns per centimeter along axis of arms in and II will help in adjusting the proportion of the stray flux to the flux flowing through arms l2.

Referring to Fig. 6, there is shown a perspective view of the arrangement with a cathode ray tube. The yoke arms 10 and II, with the appurtenant pole-pieces l2, are shown with windings i3 and 5 i4 wound about arms i0 and II respectively. The field from the pole-pieces thus interacts with the fields from the coils, and forms a field which is substantially homogeneous. A cathode ray tube 20 has an electron gun structure M which is adapted to develop and concentrate and accelerate a cathode ray beam which will be deflected onto various portions of the screen 22 by means of the deflection apparatus shown.

What we claim is:

1. In electron beam apparatus wherein there is developed an electron beam, said beam being linearly deflected along a predetermined path, apparatus for deflecting said electron beam comprising a plurality of co-operating pole members each adapted to embrace a portion of the path of deflection of said beam, and means for establishing a flux between said pole members for deflecting said beam, said latter means being positioned at a finite distance from said pole pieces so that the electromagnetic field from said latter means intersects the flux from said pole pieces for establishing a substantially equal field intensity along the line of deflection of said beam.

2. In electron beam apparatus wherein there is developed an electron beam, said beam being linearly deflected along a predetermined path, apparatus for deflecting said electron beam comprising a plurality of co-operating pole members each adapted to embrace a portion of the path of deflection of said beam, and means comprising a plurality of inductive windings for establishing a flux between said pole members for deflecting said beam, said latter means being positioned at a finite distance from said pole pieces so that the electromagnetic field from said latter means intersects the flux from said pole pieces for establishing a substantially equal field intensity along the line of deflection of said beam.

3. In electron beam apparatus wherein there is developed an electron beam, said beam being linearly deflected along a predetermined path, apparatus for deflecting said electron beam formations comprising a yoke member, a plurality of magnetic pole members joined to said yoke means, each of said poles being adapted to embrace a portion of the path of deflection of said beam formation, and means for establishing a flux between said pole members for deflecting said beam, said latter means being positioned at a finite distance from said pole pieces so that the electromagnetic field from said latter means intersects the flux from said pole pieces for establishing a substantially equal field intensity along the line of deflection of said beam.

4. In electron beam apparatus wherein there is developed an electron beam, said beam being linearly deflected along a predetermined path, apparatus for deflecting said electron beam formations comprising a yoke member, a plurality of magnetic pole members joined to said yoke means, each of said poles being adapted to embrace a portion of the path of deflection of said beam formation, and means comprising a plurality of inductive windings for establishing a flux between said pole members for deflecting said beam, said latter means being positioned at a finite distance from said pole pieces so that the electromagnetic field from said latter means intersects the flux from said pole pieces for establishing a substantially equal field intensity along the line of deflection of said beam.

5. In electron beam apparatus wherein there is developed an electron beam, said beam being linearly deflected along a predetermined path, apparatus for deflecting said electron beam formations comprising a yoke member having a gap therein, a pair of pole members joined to said yoke member, a pole face joined to each of said pole members, said pole faces having such a configuration that one edge of a pole face is closer to the other pole face than is the other edge thereof, and means for establishing a flux between said pole faces for deflecting a beam formation, said latter means being positioned at a finite distance from said pole faces so that the electromagnetic field from said means intersects the furtherest spaced pole face edges without intersecting the other edge of said pole face for establishing a substantially equal field intensity at all points along the line of deflection of said beam.

HANS OTTO ROOSENSTEIN. HORST I-IEWEL. 

